REPLIGEN CORP

Disclosure Controls and Procedures

The Company’s management is responsible for establishing and maintaining adequate disclosure controls and procedures (as defined in Rules 13a-15(e) or 15d-15(e) under the Securities Exchange Act of 1934 (“Exchange Act”)). Disclosure controls and procedures are those controls and procedures that are designed to ensure that information required to be disclosed in the Company’s reports filed or submitted under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commissions’ rules and forms, and that such information is accumulated and communicated to the Chief Executive Officer and Chief Financial Officer, as appropriate, to allow timely decisions regarding required disclosures.

Under the supervision and with the participation of the Company’s management, including the Company’s Chief Executive Officer and Chief Financial Officer, the Company carried out an evaluation as of September 30, 2026, of the effectiveness of the design and operation of the Company’s disclosure controls and procedures pursuant to Exchange Act Rules 13a-15(b) and 15d-15(b). Based on such evaluation, the principal executive officer and principal financial officer have concluded that, as of the end of such period, the Company’s disclosure controls and procedures were not effective because of the previously reported material weaknesses in our internal control over financial reporting, which are described in Part II, Item 9A, “Controls and Procedures” of our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which was filed with the Securities and Exchange Commission on February 26, 2026 (“Form 10-K”). Notwithstanding the material weaknesses, the Company’s Chief Executive Officer and Chief Financial Officer have concluded that the unaudited condensed consolidated financial statements included in this Quarterly Report on Form 10-Q are fairly stated in all material respects in accordance with generally accepted accounting principles in the United States for each of the periods presented.

Material Weaknesses in Internal Control Over Financial Reporting

A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of the Company's annual or interim financial statements will not be prevented or detected on a timely basis. As previously disclosed in the Form 10-K, the Company identified the following material weaknesses in internal control over financial reporting:

•Management did not maintain effective information technology (“IT”) general controls for information systems that are relevant to the preparation of our financial statements. Specifically, we did not maintain logical access controls and program change management controls to ensure that access to programs and data are appropriately restricted and program and data changes are identified, tested, authorized and implemented appropriately. As a result, automated and business process controls that rely on information from the systems were also deemed ineffective because they could have been adversely affected.

•Irrespective of the effects of the IT general controls deficiencies, management did not perform certain business process-level controls related to inventory valuation and the financial statement close process either in a timely manner or with an appropriate precision threshold.

As of September 30, 2026, the Company has not remediated these material weaknesses. In connection with the remediation plan previously disclosed in the Form 10-K, the Company performed remediation activities during the nine months ended September 30, 2026, as detailed below.

Remediation Plans

IT General Controls -During the nine months ended September 30, 2026, our remediation activities included the following with respect to IT general controls:

•Continued execution of controls that we worked to improve during fiscal year 2025 that did not have a sufficient period of time to demonstrate operating effectiveness as of December 31, 2025;

•Engaging third-party experts to assist in certain aspects of the remediation plan;

•Redesigning certain existing controls with additional attributes to mitigate the presumed IT risk relevant to the control;

•Evaluating, enhancing, and adding personnel in the IT organization with a focus on the requisite experience in the areas of internal control compliance; and

•Assessing and identifying areas within logical access where supplemental tools can be implemented to enhance role security and logical access controls compliance.

Business process-level controls related to inventory valuation and the financial statement close process- During the nine months ended September 30, 2026, our remediation activities included the following with respect to certain business process-level controls related to inventory valuation and the financial statement close process:

•Continued execution of controls that we worked to improve during fiscal year 2025 that did not have a sufficient period of time to demonstrate operating effectiveness as of December 31, 2025;

•Redesigning and executing enhanced controls related to inventory valuation;

•Engaging third-party experts to assist in certain aspects of the remediation plan;

•Initiating the implementation of software tools in fiscal year 2026 to support control monitoring activities and the retention of control documentation; and

•Provided ongoing training related to internal control over financial reporting for control owners.

We believe we are making progress toward achieving effectiveness of our internal control over financial reporting. The actions that we are taking are subject to ongoing management review and Audit Committee oversight. We will not be able to conclude whether the steps we are taking will fully remediate the material weaknesses in our internal control over financial reporting until we have completed our remediation efforts and subsequently evaluated their design and effectiveness over a sufficient period of time, and management concludes, through testing, that these controls are operating effectively. We may also conclude that additional measures are required to remediate the material weaknesses in our internal control over financial reporting.

Changes in Internal Control

Except for the material weaknesses described above, there have been no changes in our internal control over financial reporting identified in connection with the evaluation required by paragraph (d) of Exchange Act Rule 13a-15 or Rule 15d-15 that occurred in the three months ended September 30, 2026, that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.